1. Field of the Invention
The present invention is directed to a radiation detector of the type having a scintillator as well as a photodiode array, whereby an electrical connection is provided from the photodiode array to measuring electronics.
2. Description of the Prior Art
A radiation detector of the above type is disclosed in German OS 197 27 219. FIG. 1 herein as well as FIGS. 2 and 3 herein, which are taken from German OS 197 27 219 are used below for explaining problems addressed by the subject matter of the present invention.
The computed tomography apparatus shown in FIG. 1 has a measuring unit composed of an x-ray source ray I that emits a fan-shaped x-ray beam 2 and a radiation receiver 3 that is composed of a series of individual detectors, for example of 512 individual detectors. The focus is referenced 11. The patient 4 to be examined lies on a patient bed 5. For scanning the patient 4, the measuring unit 1, 3 is rotated around a measuring field 9, in which the patient 4 lies by 360xc2x0 . The rotational axis is referenced 10. The x-ray source 1 that is supplied by a voltage generator 6 is operated to emit pulsed or continuous radiation. Given predetermined angular positions of the measuring unit 1, 3, sets of data are generated that are supplied from the radiation receiver 3 to a computer 7 that calculates the attenuation coefficients of predetermined picture elements from the generated data sets and visually reproduces these on a viewing monitor 8. Accordingly, an image of the transirradiated slice of the patient appears on the viewing monitor 8.
FIG. 1 also shows a gantry 14 on which the x-ray source I and the radiation receiver 3 are mounted. The rotation of the x-ray beam 2 ensues by means with of a drive mechanism 15 which engages the gantry 14.
The radiation receiver 3 is only schematically shown in FIG. 1. FIGS. 2 and 3 show the structure thereof in greater detail. As can be seen in FIG. 2 a number of individual detectors 16 are held in a formed part 17 composed of plastic, preferably an injection molded part, having a surface on which interconnects 18 are applied at both sides. Detector arrays can also be provided. Further, electronic components 19 (for example, ICs) are mounted on the formed part 17, these being electrically connected to one another by interconnects 18. The individual detectors 16 are also electrically connected to the electronic components 19 by the interconnects 18 on the formed part 17. The formed part 17 accordingly serves the purpose of holding the components 16, 19 and for their electrical connection.
As can be seen in FIGS. 1 and 3 the radiation receiver 3 is subdivided into individual detectors transversely relative to the rotational axis 10 as well as in the direction thereof, so that the simultaneous scanning of a number of slices of the patient 4 is enabled. The individual detectors 16 are connected to the interconnects 18 on the formed part 17 by contacts 20. A scintillator 21 for the conversion of the x-rays into visible light lies in front of the individual detectors 16, this visible light being converted into corresponding electrical signals by the individual detectors 16, fashioned as semiconductor detectors.
As can be seen from FIG. 2 the radiation receiver 3 is constructed of a number of modules 22, each module thereof comprising a formed part 17 with the components 16, 19. For example sixteen individual detectors 16 can thereby be provided per module, with a total number of, for example, 512 individual detectors being provided by thirty-two such modules 22. The modules 22 can be electrically connected to one another via cables 23 that are connected to molded plugs 24.
FIG. 3, which shows a view in the direction of the arrow III in FIG. 2, shows that the formed parts 17 are angled, with the individual detectors 16 mounted at the outside on the upper leg, and the electronic components 19 mounted in the inside of the angle. Some of the electronic components 19 are arranged on an inward projection 25. The angle is thereby closed by a covering 26, so that a box-shaped overall profile is produced (in cross-section) for the acceptance of the electronic components 19. A carrier plate 27 carries the modules 22 which are held thereon by catches 28. An adjustment (shim) fit pin 29 serves the purpose of aligning the shaped parts 17 to the focus 11 of the x-ray source 1.
An object of the present invention is to provide a radiation detector of the type initially described which can be economically manufactured while still achieving reliable electrical connections between the photodiode 3 and the measuring electronics.
This object is inventively achieved in a radiation detector having a scintillator and a photodiode array wherein a transparent film with interconnects is arranged between the scintillator and the photodiode array for the electrical connection of the photodiode array to a measuring electronics. As a result, particularly good electrical connections can be effected in a very tight space.
It is especially advantageous for the transparent film to be placed into connection with the measuring electronics via contact pads, since the photodiode array then can be electrically tested independently of the measuring electronics.
It is also advantageous for the transparent film with the contact pads to be placed into connection with the contacts of the measuring electronics by at least one resilient biasing element, since an easier replacement of the photodiode array as well as replacement of the measuring electronics are thus possible.
When photodiode arrays are arranged in a number of lines, then a number of slices can be scanned given a single transirradiation of an examination subject. Preferably, the scintillator has a ceramic substrate, particularly when the scintillator is a scintillating ceramic, and advantageously this scintillating ceramic carrier has individual tiles that are arranged in at least one row. Cross-talk, i.e. the transfer of light from one tile to another tile, is thus reduced, and as a result the resolution of the radiation detector is increased. In order to suppress the cross-talk, a reflector can be disposed between the tiles.